The present invention concerns a packaging container manufactured through fold forming or other processing to shape a plastically deformable, flexible material, of the type which exhibits a tubular container body with two or more longitudinal edges which delimit between them in pairs a mainly flat side wall in the container.
A packaging container of the type which is described above is known through EP-A-O 353 991 and EP-A-O 353 496. The material in these known packaging containers exhibits one or more skeletal layers of plastic and filler mixed in the plastic, and possibly also one or more further layers laminated to the skeletal layer with the aim of giving the material the desired sealing properties, e.g. an Al foil which gives the material excellent gas-tight properties.
The known packaging containers are manufactured either from a strip of from a prefabricated substance of the material, through fold forming and sealing with the aid of modern, rational packaging machines of the type which both shapes, fills and closes the finished packagings.
From, for example, a strip with a pattern of fold lines facilitating fold forming and a decoration in line with the pattern of fold lines, packaging containers are manufactured through the strip first being shaped into a tube through the two longitudinal edges of the strip being joined to each other in an overlap joint. The tube is filled with the contents in question and divided into closed, filled packaging units through repeated transverse sealings of the tube across the longitudinal direction of the tube below the level of contents of the tube. The cushion shaped packaging units are separated from each other through cuts in the transverse sealing zones and given the desired geometric, generally parallelepiped-shaped final form through a final shaping and sealing operation during which the two upper double-wall triangular corner flaps of the packaging containers are bent down towards and sealed to the packaging container's respective adjacent side walls and the two lower double-wall triangular corner flaps of the packaging containers are bent in towards and sealed to the packaging container's flat bottom. A well known example of such a parallelepiped shaped packaging is Tetra Brik (reg. trade mark).
From a prefabricated flat material provided with fold lines a, packaging containers are manufactured through the material first being formed into a tube with square, rectangular or any other desired cross section through the two opposite sides of the material being joined to each other in a longitudinal overlap joint. One end of the tube is given any form of bottom closure through fold forming and sealing of the bottom field of the material delimited by means of fold lines. The tube provided with a bottom is filled with the desired contents through its open top end which is thereafter closed through what is known as bellows folding of the corresponding top field delimited by means of fold lines to form a roof ridge shaped top closure (known as gable top). A well known example of such a packaging container is Tetra Rex (reg. trade mark).
From a prefabricated material provided with fold lines and a decoration, packagings of the known type Tetra Top (reg. trade mark) are also manufactured. The packaging containers are manufactured through two opposite sides of the material being joined to each other in an overlap joint to form a tube with square, rectangular or any other desired cross section, after which the top end of the tube is closed with the aid of a plastic lid which is injection molded in place and, through surface fusion with the plastic in the material of the tube, is joined to the end of the tube in a mechanically strong, liquid-tight sealing seam around the whole opening contour of the end of the tube. The tube thus closed is filled with the contents in question and given any form of bottom closure through fold forming of the bottom field of the material delimited by means of fold lines.
From a plastically deformable, flexible material of the type described in, for example, the two previously mentioned European patent applications, packaging containers can also be produced through other mechanical shape processing than fold forming. For example containers provided with a bottom are manufactured through injection moulding or vacuum forming processes in which flat material is shaped with the aid of vacuum which pulls the material against mould surfaces in a vacuum mould shaped according to the desired container shape.
Whether the packaging container is manufactured through fold forming, vacuum forming, injection moulding or some other mechanical shape processing, it is usual for the container produced to exhibit two or more longitudinal edges which delimit between them in pairs mainly flat side walls or parts of walls. A packaging container of the type Tetra Brik or Tetra Rex thus has four longitudinal edges which delimit four flat side walls facing each other in pairs, while a packaging container of the type Tetra Top can have four longitudinal edges which delimit at the lower end of the packaging containers four wall sections facing each other in pairs which change in an upward direction into a tubular part of the container with a circular or other edgeless cross section.
The requirement set for these so-called disposable packaging containers is that they must be easy to manufacture and easy to handle in both transport and use and that they must be sufficiently rigid in form and stable in dimensions to resist external stresses to which the packaging containers are subjected during normal transport and handling. For example the packaging containers must be able to be gripped easily with the hand around two longitudinal edges serving as grip supports without the risk of the packaging container wall being deformed or cracked under the pressure of a grip by a hand. Even if the known packaging containers are normally sufficiently mechanically strong and form stable to resist external stresses during transport and handling connected with it, it not infrequently happens that the side walls of the packaging containers used as gripping surfaces are seriously deformed towards the longitudinal gripping edges and/or that the edges are cracked and thereby make the packaging container impossible to handle or very difficult to handle when it is gripped and lifted in conjunction with its being emptied of its contents. The problem can be avoided through making the packaging wall thicker, but this would entail reducing the packaging material's flexibility and with it the material's formability, with fold forming of the material made more difficult as a result. An increase in the material thicknesses would also entail an increased material consumption and thereby increased material cost for the packaging container.